1. Technical Field
The present invention relates to developing devices and image forming apparatuses.
2. Related Art
As a developing device which performs development using toner particles, there is known a developing device including a toner-particle bearing roller which is for developing a latent image by bearing toner particles contained in a toner particle containing element.
In order to charge toner particles and to restrict the layer thickness of toner particles borne by the toner-particle bearing roller, such a developing device is furnished with a layer-thickness restriction member which abuts against the toner-particle bearing roller bearing the toner particles. A surface of the toner-particle bearing roller is sandblasted and has fine recesses and projections thereon. Toner particles are borne by the toner-particle bearing roller on the surface thereof and are pressed by the layer-thickness restriction member, and consequently the toner particles are charged by rolling while being rubbed by the surface having the recesses and projections or by the layer-thickness restriction member.
In such a developing device, if the recesses and projections of the surface of a toner-particle bearing roller are formed by sandblasting, the recesses are not uniform in size, depth, shape, and arrangement. Therefore, toner particles having entered a deep recess may not be charged satisfactorily because the toner particles are not caused to roll, for example. As mentioned above, due to non-uniformity of the recesses and projections on the surface of the toner-particle bearing roller, there are cases in which toner particles may not be charged satisfactorily in some areas or toner particles caught in small recesses may cause filming. Besides, if toner particles are not charged satisfactorily, there have been problems that the toner particles may spill from the developing device and result in scattering of the toner particles to the inside of an image forming apparatus, and that fog may occur in an image.
Note that JP-A-2003-263018, JP-A-1-102486, and JP-A-2005-84533 are examples of a related art.